1. Field of the Invention
The present invention relates to a focal plane shutter for cameras having one or two shutter blades.
2. Description of the Related Art
In focal plane shutters for cameras, one type in which two blade rooms are constituted between plate components of three sheet components called the shutter base plate, the middle plate, and the auxiliary base plate, and two shutter blades in which so called the first blade, and the second blade are arranged individually in the blade rooms, and another type in which one shutter blade is arranged in a blade room constituted between the shutter base plate and the auxiliary base plate have been known. The former type of the focal plane shutter can be used for a silver halide film camera as well as for a digital camera. However, the latter type of the focal plane shutter can be used only for a digital camera.
In any case of the focal plane shutters, constitutions of the shutter blades are almost same, and it is constituted by two or more arms, an end of the length direction of which is attached rotatably to the shutter base plate, and at least one blade which is pivoted by the arms. And, one of the arms is connected with a drive pin of a drive component rotatably attached to a shutter base plate, and is swung by the drive component, and an exposure aperture is made open and close by the blade.
As the drive component, for example, as shown in Publication of the Japanese unexamined patent application, Toku Kai.No. 2000-2907, and Japanese published unexamined patent application Toku Kai Hei No. 1-280739, it is rotated by the energized power of a drive spring to one direction, and to another direction, it may be rotated by a set component attached rotatably to a shutter base plate. However, recently, for example, as shown in Publication of the Japanese unexamined patent application, Toku Kai. No. 2004-101860, using of an electromagnetism actuator as a driving source has been also known. In that case, a component formed in one with a rotor made of permanent magnet is used as a drive component, and the drive pin is arranged on the rotor.
As mentioned above, in all cases of the focal plane shutter, besides the arm, the drive component and the set component, two or more attachment shanks for supporting of various rotation components so as to enable to be rotated are installed upright on the shutter base plate in order to rotate smoothly a rotation component, lubricant, grease, or the like is applied on those attachment shanks if needed. Particularly, for the drive component, a high speed and a stable rotation are required, and for the set component, rotation with low torque when setting is made. However, as well known, since a big power is applied to the drive component attachment shank and the set-component attachment shank to the radial direction, the attachment shanks are manufactured thicker than those of the other attachment shanks. Therefore, in order to reduce friction between the components and the attachment shanks and to raise durability, lubricant has been applied between those in many cases so far. In Japanese published unexamined patent application Toku Kai Hei No. 2000-2907, a constitution in which a groove for sump is formed annularly to a drive component attachment shanks and a blade attachment shank formed in one to the drive component attachment shank has been shown.
By the way, it is obvious that the attachment shank of the drive component shown in the publication of the Japanese unexamined patent application, Toku Kai No. 2000-2907 is made of metal, although no material is specified. Therefore, the attachment shank is installed upright to the shutter base plate by caulking processing, etc. However, recently, synthetic resin has been used for shutter parts remarkably, and it has been used not only for major parts such as a drive component and a set component, but also for almost of shutter base plate. Under such circumstance, attachment shanks of a drive component and a set component have been made of synthetic resin. In Japanese published unexamined patent application Toku Kai Hei No. 1-280739, an example of the shutter for cameras in which those attachment shanks are manufactured by simultaneous integral molding by synthetic resin material together with a shutter base plate has been shown.
Main problems when the integral molding of a shutter base plate and the attachment shank of rotation components is carried out simultaneously by synthetic resin material, is whether melting material poured in from a gate is filled suitably in a die, and a long and slender attachment shank is formed in predetermined form or not at the time of manufacture and after the time of manufacture, it is whether the attachment shank is inclined or destroyed by an external force, and heat deformation is caused or not. Then, in Japanese published unexamined patent application Toku Kai Hei No. 1-280739, it has been proposed that a considerable large area in near a part in which an attachment shank is installed upright is formed so as to have large wall thickness over the both sides of the front surface and the back surface of the area as a solution of such problems.
However, it cannot be said that such solution is good enough. Especially, in cases of a camera using film of APS (Advanced Photo System), and a focal plane shutter used for a digital camera using a solid state image pickup device having small imaging area, it is necessary to make the attachment shank thin as an exposure aperture becomes small, Therefore, there is a problem such that when the simultaneous integral molding is carried out, synthetic resin material does not flow suitably to a shank part from a base plate part, and a predetermined form and intensity cannot be easily obtained. Furthermore, by such solution mentioned above, it is substantially the same as the shutter base plate is made thick, and accordingly a size of the whole shutter in a direction along the optical shanks becomes large, and furthermore the space of a blade room also becomes large. Therefore, it becomes necessary to take another measures for stable run of the shutter blade, etc., which are derivative problems.
Recently, the attachment shanks of various rotation components are also manufactured by the synthetic resin material together with the base plate, and it has been fabricated by the synthetic resin material to the metal base plate. However, if an attachment shank is made of the synthetic resin in such ways mentioned above, for example, as shown in the publication of the Japanese unexamined patent application, Toku Kai No. 2000-2907, it becomes very difficult to form a groove for sump having annular shape. For example, as shown in publication of the Japanese unexamined patent application, Toku Kai Hei. 1-280739, when the attachment shanks are manufactured by the simultaneous integral molding together with the shutter base plate, usually, after the synthetic resin material is poured into a mold cavity, two main dies are separated in the thickness direction (direction of shank of an attachment shank) of the shutter base plate. Therefore, in order to form a groove annular as mentioned above, it is necessary to arrange further at least two slide dies, and to make them slide relatively in the direction which intersects perpendicularly with the direction of separation of the two main dies when the dies are separated.
Therefore, there is the other problem that cost becomes high by effects such that the structure of the whole dies not only becomes complicated by increasing parts of the dies in number, but also it becomes difficult to carry out two or more product-processing (picking of a plurality of products) by single shot, and to necessitate a high-class molding machine. Furthermore, when complicated slide dies are used in such way mentioned above, there is a problem such that a mark of a parting line is formed by the joint of two slide dies to the direction of the fabricated attachment shank, and it is not appropriate, as the attachment shank for rotating smoothly rotation components, such as a drive component and a set component.